All of the U.S. patents cited throughout this specification are hereby entirely incorporated herein.
Ultraviolet absorber compounds have been utilized for a number of protective applications, including within compositions for covering skin, on and within apparel and other types of textiles, within transparent plastic containers, and the like, to combat the harmful and degradable effects of certain wavelengths of light in the UV spectrum. The best known UV absorbers are benzotriazoles, available from Ciba under the tradename Tinuvin®, and benzophenones, available from Cytec Industries under the trademark Cyasorb™. Such compounds are highly effective in their UV absorber capacity; however, they are quite costly, can prove difficult to incorporate within different target media, and tend to migrate from within certain types of media (such as plastics). Furthermore, these two well known types of UV absorbers present handling difficulties in that they are generally produced and utilized in powder form and have relatively low melting points. Particularly, within plastic media, the powder form of these compounds is problematic; a liquid is much easier to handle, does not require melting, and provides more effective and thorough mixing throughout the target plastic. Additionally, these previously utilized UV absorbers provide UV protection over a relatively narrow range of wavelengths ({circle around (2)}max from about 290 to about 340 nm for benzotriazoles; from 260 to 300 nm for benzophenones), which ultimately leaves a potentially damaging range of unprotected UV exposure (to about 400 nm). Attempts to increase the amount of such UV absorber compounds in order to provide potential protection over such a broader wavelength range is ineffective, not to mention such greater amounts of UV absorbers increases the production of unwanted colorations within target clear plastics and other like applications such that masking compounds (e.g., bluing agents, for example) must be utilized in relatively high amounts to combat the discoloring effect. Thus, there exists a need to provide a highly effective, liquid ultraviolet absorber which exhibits a versatility to be incorporated within or applied to different and various media and substrates and which, alternatively, can provide protection over the range of wavelengths in the UV spectrum of from about 290 to about 400 nm (in order to provide the best overall protection from possible harm and/or degradation associated with UV exposure).
Methine-based compounds, in particular certain malonate derivatives, as in European Patent Abstract 350–386-A, to L'Oreal SA, are useful as UV absorbers in cosmetic sunscreen compositions, are generally inexpensive to make, and provide UV protection in the spectrum from about 280 to about 360 nm. However, such compounds are highly soluble in organic solvents and would therefore easily migrate from solid compositions, such as plastics, upon introduction therein. Thus, although the utilization of an effective UV absorber, such as a malonate derivative, within plastics, may be highly desirable, such has never been taught nor fairly suggested within the prior UV absorber art due to the great difficulty in producing such a stable, and thus highly effective, UV absorbing composition from such a methine-based source. There exists a need then to produce an inexpensive UV absorber which exhibits the requisite ability to remain within media such as thermoplastics and the like (as noted above), and thus provide necessary and desirable protection from degradation due to UV exposure.
Further developments for the ultraviolet protection of certain polymeric media (such as polyesters) have included methine-based compounds which, to be effective in terms of low extraction from such a thermoplastic, must be introduced during the actual polymerization reaction of the base thermoplastic polymer itself. For example, U.S. Pat. No. 4,617,374 to Pruett et al. teaches such UV absorbers for polyester end-uses. Again, however, such compounds exhibit very high extraction results unless they are added as to-be-polymerized reactants themselves with the ester monomers during the polymerization step. In such an instance, these UV absorbers are actually integrated within the polymer, and not just mixed within the thermoplastic medium. As such, although such compounds do exhibit excellent results when polymerized within the target polyester, unfortunately such compounds are limited in their versatility since the only time during which effective introduction is permitted is during the aforementioned polymerization procedure. There thus still remains a need to provide a more versatile UV absorber for thermoplastic end-uses such that the producer can introduce the UV absorber at any time during the production of the target thermoplastic such that the additive does not exhibit such high extraction and yet still provides excellent UV absorbing properties thereto.
It has now been found that through the addition of polyoxyalkylene chains onto certain ultraviolet absorber compounds, greater versatility of potential uses for the new UV absorber is provided, particularly in terms of the needed low-extraction as noted above. Therefore, it has been found that such polyoxyalkylenated compounds (such as those, without intending to limit the breadth of the invention, the methine-based compounds utilizing vanillin and resorcinol as starting materials) provide UV absorbers which are highly effective in filtering harmful UV-A and UV-B rays over a broad spectrum ({circle around (2)}max from about 280 to about 400 nm, more preferably from about 320 to about 400 nm). Furthermore, it has been found that in combination with a benzotriazole and/or a hydroxybenzophenone, or other similar type of UV absorber compound, the resultant composition is accorded protection from a great amount of potentially damaging UV radiation (from approximately 250 to about 400 nm). Additionally, such a combination is highly stable within the desired media, and thus provides long-term protection to the desired sample stored within the target treated plastic article. Additionally, such compounds are very low in color when prepared in accordance with certain procedures, most notably with certain alkoxylation catalysts, including, without limitation, metal hydroxides and other bases, both alone and in the presence of amine-based alkoxylation catalysts (particularly with affinities for available protons), as well as rare earth phosphate salts, such as those taught within U.S. Pat. Nos. 5,057,627, 5,057,628, 5,059,719, 5,118,870, 5,208,199. Such low-color alternatives thus provide the basis for effective utilization within colorless (clear and transparent) applications, such as the desired clear plastics, while simultaneously providing the necessary effective UV protection.
Although some interest has been demonstrated within the area of certain methine-based UV absorber compounds (i.e. L'Oreal's malonate derivatives), to date there has been no disclosure or fair suggestion regarding the utilization of the polyoxyalkylenated derivatives of such UV absorbers in that capacity within certain media (such as, for example, plastics), or on other surfaces (skin, textiles, for example), or in other applications (inks, and the like, for example). In particular, no disclosures exist concerning low-color, low-extraction (migration) polyoxyalkylenated UV absorber compounds that provide effective protection from UV exposure between the wavelengths of from about 320 to about 400 nm. There is thus a great need within the UV absorber market, and most particularly within the transparent plastic film and container markets (for storing and protecting food, pills, and the like) for such types of improvements associated with relatively inexpensive materials and processes provided by the inventive polyoxyalkylenated methine-based UV absorber compounds. Other ultraviolet absorbing compounds and compositions have been developed or modified for certain plastic (thermoplastic, thermoset, etc.) applications, such as a class of compounds known by the name of Tinuvin®, available from Ciba, and noted above. Although such compounds appear to provide very good ultraviolet protection both to the plastic itself and to any stored liquids, solids, etc., within a container made therewith such plastics, unfortunately such a class of compounds exhibits undesirable or problematic deficiencies. In particular, the breadth of protection within the UV spectrum is generally limited to from about 320 to about 375 nm with such compounds. Thus, they generally do not provide adequate UV protection to contents of plastic packaging over the entire range of UV wavelengths. Also, such Ciba compounds are generally naturally solid in nature and thus are either dispensed within target resins as solid powders or must be dispersed within liquids by the end-user at time very close to dispensing in order to be effective. If any such Ciba UV absorbers are in fact liquid, they still are limited in their breadth of UV protection in terms of wavelength ranges. Lastly, such Ciba compounds exhibit relatively high extraction levels and migratory characteristics from within target plastic resins, particularly thermoplastics such as polyethylene terephthalates. Thus, although such compounds are effective for UV protection to a certain extent, there are a number of drawbacks for which improvements are highly desired and necessary. To date, there thus remains a great need to provide an effective UV absorber that eliminates the above-noted deficiencies.